The present invention relates generally to the field of communication systems and more particularly to wireless communication systems.
As wireless communication systems such as cellular telephones networks have become more common, the emphasis in wireless communication systems is to provide feature rich services in a mobile (wireless or cellular) environment. The mobile-to-mobile calling patterns are expected to increase exponentially as more subscribers are added to wireless services.
This produces a need for a network infrastructure in existing communication systems that supports both the existing connectivity paths and those new connectivity paths required to support a substantially higher mobile-to-mobile traffic percentage. Presently, wireless network infrastructures have an inherent need to convert between the radio frequency (RF) modulated encoded speech frames of a transmitting mobile unit (transmit unit), such as a cellular telephone, and the 64 kilobit per second (64 kb) pulse code modulation (PCM) based telephony infrastructure of existing switching equipment. In order to complete the mobile-to-mobile connection, the exact process occurs in the reverse direction requiring the conversion of 64 kb PCM into RF encoded speech-frames for the receiving mobile unit (receive unit). This conversion occurs multiple times in a mobile-to-mobile call scenario. Thus, conversion delay is introduced into the end-to-end path (transmit unit to receive unit) and quantization noise is increased to level that are highly noticeable to the mobile users.
Additionally, new hardware is required because the wireless infrastructure requires additional trunk resources to connect both ends of the mobile-to-mobile call. Thus, a need exists for network infrastructures that support existing connectivity paths and provide new connectivity paths to support a higher mobile-to-mobile traffic percentage.
In accordance with the present invention, the problem of multiply converting the RF modulated encoded speech-frames, received from the transmit unit, into an intermediate 64 kb PCM and then back to RF modulated encoded speech-frames for transmission to the receive unit is overcome by using an interface circuit that is programmable and has a matrix component that allows similar encoded speech-frame streams to cross-connect and differently encoded speech-frame streams to be cross-converted without any intermediate steps.
An example system of the invention includes a transmit unit that transmits an input signal of an input modulation encoded speech-frame type, a receive unit that receives an output signal of an output modulation encoded speech-frame type and a direct interface system that directly interfaces the input signal to the output signal.
The direct interface system includes a transmit interface circuit that directly interfaces the input signal to a data-path signal and a receive interface circuit that directly interfaces the data path signal to the output signal.
The transmit interface circuit includes both a plurality of input modulation encoded speech-frame types and a plurality of output modulation encoded speech-frame types. One of the input modulation encoded speech-frame types represents the encoded speech-frame type of input signal and one of the output modulation encoded speech-frame types represents the encoded speech-frame type of output signal. Additionally, the transmit interface circuit include an interface matrix that directly interfaces the encoded speech-frame type of the input signal to the encoded speech-frame type of the output signal.